<!-- a in a -->

<template>
  <div><u-button>click
    <m-popper>
        <a href="/" target="_blank">popper</a>
    </m-popper>
</u-button>
<u-button><a href="/" target="_blank">abc</a></u-button>
<u-button><div><a href="/" target="_blank">abc</a></div></u-button>
<a><div><a href="/" target="_blank">abc</a></div></a></div>
</template>